To have the script run as root, you either need to be root when you execute it (or from root's crontab), or use sudo when the script is executed.

As almut said, use system commands for most of the work. Just plan out how you would do it on the command line, then wrap those commands in Perl using one of the many methods (system, exec, backticks)... which one you use depends on various things, like do you want the script to wait for that command to finish before continuing, etc. You can read up on those commands just about everywhere. The easiest way is to google 'perl <command>'.